Testers for the testing of circuit boards may in principle be divided into two groups, those with finger testers and those with parallel testers. The parallel testers are testers which, by means of an adapter, contact simultaneously all or at least the majority of circuit board test points of a circuit board to be tested. Finger testers are testers for the testing of non-componented or componented circuit boards, which scan the individual contact points sequentially using two or more test fingers.
In the testing of non-componented printed circuit boards, as compared with the testing of componented circuit boards, i.e. in-circuit testing, it is necessary to contact significantly more circuit board test points. For this reason the main criterion for successful marketing of a finger tester for non-componented printed circuit boards is the throughput of contacted circuit board test points within a predetermined period of time.
The test fingers are generally fixed to a slide which is able to traverse along a cross-bar, while the cross-bars are in turn guided and able to traverse on guide rails. The slides may thus be positioned at any desired point on a test array which is usually rectangular. To contact a contact point of a circuit board to be tested, the slide is able to move vertically on the cross-bar, so that the test finger may be placed on the contact point from above or from below.
A finger tester is described in EP 0 468 153 A1 and a method of testing circuit boards using a finger tester is described in EP 0 853 242 A1.
JP 02-130477 A discloses a method of testing circuit boards using a finger tester with one test finger which is automatically traversed to contact circuit board test points of a circuit board to be tested. The test finger has a test probe with two contact tips. Using the two contact tips and a contacting sensor, the point in time is determined at which the test probe makes contact with a circuit board test point of the circuit board to be tested. The level of the surface of the circuit board test point is determined with the aid of this point in time and the position of the probe tips.
U.S. Pat. No. 4,926,345 discloses an apparatus for the trimming of conductor paths. This involves the conductor paths being cut to the desired width by means of an automatically traversing cutter. However, before cutting take place, the course of the conductor path and also a vertical profile of the circuit board are determined by means of a sensor, so that the cutting operation may be performed with the desired accuracy.
U.S. Pat. No. 5,489,855 describes a finger tester with several test fingers.